[Dns] added RetryExecutor

Author: arnaud-lb

Query/RetryExecutor.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace React\Dns\Query;
+
+class RetryExecutor implements ExecutorInterface
+{
+    private $executor;
+    private $cache;
+    private $retries;
+
+    public function __construct(ExecutorInterface $executor, $retries = 2)
+    {
+        $this->executor = $executor;
+        $this->retries = $retries;
+    }
+
+    public function query($nameserver, Query $query, $callback, $errorback)
+    {
+        $this->tryQuery($nameserver, $query, $callback, $errorback, $this->retries);
+    }
+
+    public function tryQuery($nameserver, Query $query, $callback, $errorback, $retries)
+    {
+        $that = $this;
+        $errorback = function ($error) use ($nameserver, $query, $callback, $errorback, $retries, $that) {
+            if (!$error instanceof TimeoutException) {
+                $errorback($error);
+                return;
+            }
+            if (0 >= $retries) {
+                $error = new \RuntimeException(
+                    sprintf("DNS query for %s failed: too many retries", $query->name),
+                    0,
+                    $error
+                );
+                $errorback($error);
+                return;
+            }
+            $that->tryQuery($nameserver, $query, $callback, $errorback, $retries-1);
+        };
+        $this->executor->query($nameserver, $query, $callback, $errorback);
+    }
+}

Resolver/Factory.php

@@ -8,13 +8,14 @@
 use React\Dns\Protocol\Parser;
 use React\Dns\Protocol\BinaryDumper;
 use React\EventLoop\LoopInterface;
+use React\Dns\Query\RetryExecutor;
 
 class Factory
 {
     public function create($nameserver, LoopInterface $loop)
     {
         $nameserver = $this->addPortToServerIfMissing($nameserver);
-        $executor = $this->createExecutor($loop);
+        $executor = $this->createRetryExecutor($loop);
 
         return new Resolver($nameserver, $executor);
     }
@@ -32,9 +33,14 @@ protected function createExecutor(LoopInterface $loop)
         return new Executor($loop, new Parser(), new BinaryDumper());
     }
 
+    protected function createRetryExecutor(LoopInterface $loop)
+    {
+        return new RetryExecutor($this->createExecutor($loop));
+    }
+
     protected function createCachedExecutor(LoopInterface $loop)
     {
-        return new CachedExecutor($this->createExecutor($loop), new RecordCache());
+        return new CachedExecutor($this->createRetryExecutor($loop), new RecordCache());
     }
 
     protected function addPortToServerIfMissing($nameserver)